Referring to FIG. 1, a diagrammatic representation of a typical radio telescope is shown generally at 10. The radio telescope 10 is a typical radio telescope having a lower stationary pedestal 12 and an upper radio telescope base 14 mounted thereon for azimuth rotation. The radio telescope dish 16 is mounted on the radio telescope base 14 by suitable struts and vertically rotatable mounting means 18. Typically, large radio telescopes will have upper structures including the radio telescope base 14, telescope dish 16 and mounting means 18 weighing in excess of 6 million pounds. It is important that a suitable, reliable means be provided for azimuth rotation of this extremely large heavy structure relative to the stationary pedestal 12. In order to achieve the desired smooth and reliable rotation of the telescope base 14 in azimuth about the pedestal 12, hydrostatic bearings have typically been utilized.
FIG. 2 is a representation of a typical three pad hydrostatic bearing assembly. The bearing assembly is shown generally at 20. The bearing assembly 20 typically includes a bearing runner support 22 for supporting the upper bearing pads 24. A thin film of hydraulic oil in the neighborhood of three thousandths of an inch to twelve thousandths of an inch thick is provided between the bearing pads 24 and the bearing runner support 22. The bearing pads slide smoothly and relatively friction free over this extremely thin film layer. As is well known, it is extremely important that the upper surface of the runner support 22 be extremely smooth and level and that the lower face of the bearing pad 24 which rides over the runner support 22 be equally as smooth in order to maintain a uniform film of oil between the two. If the runner support 22 becomes bent or deformed in anyway, the bearing pad 24 may dig into or ground out on the runner support 22 resulting in destruction of the smooth upper runner support surface. Repairing scratches or grooves resulting from a ground out condition is a very expensive and time consuming process which is to be avoided at all costs.
In order to insure that the bearing runner support 22 provides as smooth and level a bearing support surface as possible, bearing runner support grout 26 is typically used on top of the stationary pedestal 12 to provide a suitable surface for mounting and precisely positioning the bearing runner support 22.
Of the many types of grouts available for mounting the runner support 22, a Portland cement type grout is now commonly used. Although this type of Portland cement grout is suitable in many respects for its intended purpose, problems have been encountered because of the relatively short service life of the grout ranging from months to several years. Over the period of time, the Portland cement deteriorates and cracks or crumbles thereby allowing bending or sagging of the bearing runner support and the resultant possibility of bearing pad grounding.
In order to prevent the possible diastrous grounding of the bearing support pads, the deteriorated grout must be replaced periodically. This results in lost tracking time which, in addition to material and labor costs is very expensive. It is therefore highly desirable to provide a suitable grout which will not deteriorate for as long a time as possible.
It is believed that deterioration of grout is mainly due to the continual extreme pressure loading and unloading at various areas around the runner support 22 due to the continual traveling of the three bearing pads 24. Further, seepage of hydrostatic oil between runner support plates and into the grout is also believed responsible for premature deterioration of grout. The presence of seepage oil in and near the grout not only causes deterioration but is troublesome in repairing the deteriorated grout since it increases curing time of Portland cement grouts thereby increasing the amount of expensive lost tracking time.
It is therefore very desirable to provide a suitable grout which may be used in the construction of new radio telescope antennas and more importantly which may be suitable for replacing the deteriorating grout present in existing structures.